This is a common question in all job interviews. There are generally two kinds of responses: the brutally honest and damning one ("I get upset with people who don't carry their load"), and the sycophantic one ("I'm a perfectionist").

What most employers are looking for is an honest answer that is followed up with an example of something you have done to work on your weakness. For example, you can say, "My workspace tends to become extremely disorganized," as long as you follow it up with, "but recently, I've put in a lot of effort to go paperless, and I'm extremely systematic in the way I manage my email inbox."

The other secret to this question is not so much in the answer but how long you take to respond. If you answer too quickly, you might be suggesting that you already know all your worst points because they are blatantly obvious and you've been told so many times. If you take too long, it will seem as if you're searching for an answer that sounds good, doesn't make you look bad, and is something the interviewer would be happy to hear. Again, it gives the perception that you are being ingratiating rather than honest.

By the way, the best answer I've heard is, "I don't know. What do you think I'd regret in six months if I worked here?"